Diazonamide A is a mitotic spindle-disrupting agent first isolated from the marine organism Diazona angulata, having the structure:

Numerous attempts have been made to synthesize this compound and its analogs. PCT publication WO 03/106438 describes a putative synthetic route; however, the structure identified as diazonamide A provided in that publication is incorrect. U.S. Pat. No. 7,022,720 correctly discloses the structure of diazonamide A and describes the synthesis of some of its analogs through the combined use of catalytic Heck endocyclization, stereo-controlled ring-contracting Pinacol rearrangement, and indole arylation via internal photo-induced electron transfer. Generic structures of some analogs are provided. U.S. application Ser. No. 11/264,502, a continuation-in-part of U.S. Ser. No. 10/227,509 (now U.S. Pat. No. 7,022,720) was filed 31 Oct. 2005, and is published as 2006/0089397. U.S. Ser. No. 11/591,016, a continuation-in-part of U.S. application Ser. No. 11/264,502, was filed 31 Oct. 2006, and is published as U.S. application 2007/0149583.
Diazonamide A demonstrated potent antineoplastic activity. Lindquist et al. J. Am. Chem. Soc., 1991, 113:2303 2304. In HCT-116 cells, a human colorectal carcinoma line, diazonamide A exhibited GI50 values (50% growth inhibitory concentration) of less than 15 ng/ml. Diazonamide A has also been found to inhibit microtubule assembly. Cruz-Monserrate et al., Mol. Pharmacol., 2003, 63:1273-1280. An analog of diazonamide A having improved antitumor activity was disclosed in U.S. application 2007/0149583. Thus, diazonamide A and its analogs represent a promising new class of antitumor agents.
Limited aqueous solubility poses difficulties in the formulation and administration of many anticancer agents. In particular, intravenous administration of an anticancer agent with low aqueous solubility may require the infusion of a large volume of liquid in order to achieve a therapeutic dose. Increasing the solubility of anticancer agents has been an important practical objective of many drug development programs. Orally administered compounds can be relatively less soluble than those administered intravenously, but must be soluble enough to be absorbed.
One obstacle to the development of diazonamide A for pharmaceutical use is its relatively low solubility in pharmaceutically acceptable solvents, in particular water. As a result, there is a need for diazonamide analogs having improved solubility which are suitable for pharmaceutical administration. In particular, there is a desire to design diazonamide analogs having improved aqueous solubility as well as antitumor activity.